If Hollywood had its own version of Mount Rushmore for male movie stars, there’d be granite shards all over the foothills right now. Not to mention a big sign that reads Pardon Our Appearance While We Remodel.

Why? Because the great stone faces who’ve anchored the biggest action flicks and epic dramas of the past decade — among them Bruce Willis, Mel Gibson, Arnold Schwarzenegger, and Kevin Costner — seem to be eroding. Audiences stamped Costner’s The Postman ”Return to sender.” Willis’ Mercury Rising is falling fast at theaters. Warner Bros. has recruited the younger, hipper Chris Rock, 32, to prop up the conceptually wheezy prospect of Gibson’s Lethal Weapon 4. And since collecting what turned out to be an overly generous $20 million up-front paycheck (plus a merchandise cut) for last summer’s Batman & Robin, Schwarzenegger weathered heart surgery and has taken his time getting another of his $100 million behemoths off the ground.

Of course, a junior group of leading men — including Tom Cruise, 35, Brad Pitt, 34, and Will Smith, 29 — have been chipping away at the old blocks for years. Lately, though, they’ve been joined by an even more precocious generation of talents who look eminently monument-worthy.

Call this crop of largely up-from-the-indies actors the Frat Pack. Almost none of them will reach their 30th birthday by the millennium, and almost all are products of postfeminist times — many were raised primarily by a divorced or remarried mom. Typically jut-jawed (what was in that infant formula anyway?) and equally chic in scruffy duds or designer suits, they’re emotional instead of stoic on screen, and far more likely to stroke the neck of a woman than squeeze the trigger of a gun.

In addition to first-rank poster boys Leonardo DiCaprio, 23, Matt Damon, 27, and Ben Affleck, 25, this new youth corps includes Edward Norton, 28, who first made his mark as a nutcase in Primal Fear, and Ryan Phillippe, 22, who appeared in I Know What You Did Last Summer and will spend this one in the highly anticipated Studio 54.

Having done their homework in small, low-budget films (like Chris Tucker in Friday, or Affleck’s star-making internship in Chasing Amy), or majored in TV drama (Mod Squad’s Omar Epps sharpened his skills on ER and Scott Wolf continues to on Party of Five), these actors are as hip to Hollywood ways as a teen in one of Kevin Williamson’s movie scripts. Instead of starring in shoot-‘em-ups or silly, Brat Pack-style teen comedies, they prefer dramatic roles in which they — brace yourself, Ah-nuld — project vulnerability as much as strength. As pop psychologist Dr. Joyce Brothers explains: ”They’re not macho-type men; they’re softer. Women respond to that because they don’t feel they could interest a guy like Stallone, who’s more interested in tackling the world than falling into your arms.”

While spreading the post-pumpitude gospel of sexual healing, DiCaprio, Affleck, and Damon have helped scare up nearly $800 million at the box office since November (if you tally up The Rainmaker, Titanic, Good Will Hunting, and The Man in the Iron Mask), and since Hollywood always follows the money, execs and producers are falling all over themselves to hand hot scripts to these boys — or, when they’re unavailable, their Frat Pack peers.